1. Field of the Invention
This invention relates to a composition and process for the manufacture of polyester. In the process according to the invention, the polycondensation is catalysed, stabilised and accelerated by the composition.
2. Summary of the Related Art
DE 199 08 628.1 discloses a catalyst system consisting of a glycolic suspension of a fine-grained carrier substance exhibiting a large porous surface in which catalytically effective metal compounds are adsorbed in the pores. Also, phosphonic acid compounds are used as stabilizers for polycondensation. In the examples, 2-carboxyethane phosphonic acid (phosphono-propionic acid) is employed as a stabilizer. Furthermore, stabilizer is added at a different time than the catalyst and is as temporally remote as possible.
Other stabilizers, such as phosphoric and phosphorous acid, “simple” phosphonic acid esters and “simple” glycol phosphates, and carboxymethane phosphonic acid have no polycondensation accelerating effect; rather, when the phosphorus concentration is increased, the polycondensation rate decreases and the catalyst is partially blocked by the stabilizer.
DE 4432839 discloses the use of tris-triethylene glycol phosphate as a stabilizer in polyester manufacturing processes catalysed by antimony and germanium to inhibit polymer turbidity.
Polyalkylene glycol phosphate esters are known in in the art as stabilizers and with other conventional catalytic agents, such as antimony, germanium, titanium or tin, do not have an accelerating effect on the polycondensation.
In EP-A-589197, polyalkylene glycol phosphate esters are described as flame retarding co-monomers.
The effect of polyalkylene glycol phosphate ester and especially tris-triethylene glycol phosphate as polycondensation catalysts is not known.
DE 19631068 disclosed carboxy-phosphonic acid compounds as polycondensation accelerators in polyester manufacture in a concentration from 30 to 900 ppm relative to the phosphorus of the carboxy-phosphonic acid compound. The carboxy-phosphonic acid compounds effect cross-linking of the polymer chains and also protect against thermal and thermo-oxidative polymer decomposition.
It is also known that stabilizers containing phosphorus impair the activity of the catalytic agents in the esterification and transesterification phases as well as the precondensation phase because they form inactive compounds with the catalytic agents.
Furthermore, balanced, specific process methods are known in which defined catalyst and stabilizer concentrations and additive positions or additive times are controlled, wherein the addition of the stabilizer occurs after that of the catalyst.
With transesterification it is also usual to block the transesterification catalyst with an appropriate amount of a phosphorus compound to prevent the detrimental effect of the transesterification catalyst on the polycondensation. Only after this blocking is the polycondensation catalyst added, followed later by addition of the appropriate polycondensation stabilizer.
Furthermore, it is also known that in the manufacture of polyester for some applications (e.g., packaging and technical yarns) crystallization and polycondensation are carried out in solid state (U.S. Pat. No. 4,064,112, U.S. Pat. No. 4,263,425, U.S. Pat. No. 5,362,844). In other applications, fibers or filaments, for example, are spun directly or pre-forms are directly produced, wherein intermediate transition to a solid state and renewed melting of the polymer is not required.